1. Field of the Invention
The invention is generally related to the waste processing of chemical cleaning solvents and more particularly to a method for processing chemical cleaning solvent waste.
2. General Background
In many industries, the life and performance of equipment can be compromised by the accumulation of corrosion products. This is especially true for steam generators used by electrical utilities. The corrosion products appear as sludge on the tubesheet and block flow holes in tube support plates. Fouling consists of solid deposits, primarily iron, at the tube support plates and on the outside of tubes. Support plate deposits can increase pressure drop resulting in reduced steam generator performance. Tube bundle deposits can reduce heat transfer capability, also degrading performance. Buildup of these deposits can concentrate contaminants such as chlorides and fluorides which promote stress corrosion cracking. Mechanical cleaning methods such as water lancing can remove deposits from accessible areas. However, chemical cleaning is the only means to completely remove deposits in a pressurized water reactor (PWR) steam generator. A chemical solution is introduced into the secondary side during a shutdown. Then, following a soaking period, the unit is flushed. Sludge piles are removed by water lancing. Chemical cleaning of nuclear steam generators generates a large volume of solvent waste, generally seventy-five thousand to two hundred fifty thousand gallons. It then is necessary to process the chemical cleaning solvent waste to reduce to a minimum the volume of material or liquid that must be stored or disposed of so as not to release hazardous material into the surrounding environment. Technologies previously used for such processing include the following: evaporation to concentrate the solvent, solidification of the concentrate, and chemical treatment of the distillate; wet oxidation of the solvent, reverse osmosis, and chemical treatment to purify the distillate; dilution of the solvent, chemical treatment to precipitate the metals, and use of filtration and/or filter press to separate the metals; wet-air oxidation of the solvent, and solidification of the concentrate; and ion exchange of the solvents.